Guangyong Zeng

Novel polyvinylidene fluoride nanofiltration membrane blended with functionalized halloysite nanotubes for dye and heavy metal ions removal.

Membrane separation is an effective method for the removal of hazardous materials from wastewater. Halloysite nanotubes (HNTs) were functionalized with 3-aminopropyltriethoxysilane (APTES), and novel polyvinylidene fluoride (PVDF) nanofiltration membranes were prepared by blending with various concentrations of APTES grafted HNTs (A-HNTs). The morphology structure of the membranes were characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle (CA), pure water flux (PWF) and antifouling capacity of membranes were investigated in detail. In addition, the separation performance of membranes were reflected by the removal of dye and heavy metal ions in simulated wastewater. The results revealed that the hydrophilicity of A-HNTs blended PVDF membrane (A-HNTs@PVDF) was enhanced significantly. Owing to the electrostatic interaction between membrane surface and dye molecules, the dye rejection ratio of 3% A-HNTs@PVDF membrane reached 94.9%. The heavy metal ions rejection ratio and adsorption capacity of membrane were also improved with the addition of A-HNTs. More importantly, A-HNTs@PVDF membrane exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a new method for membrane modification in the field of wastewater treatment.

Novel hydrophilic PVDF ultrafiltration membranes based on a ZrO 2 –multiwalled carbon nanotube hybrid for oil/water separation

A novel hydrophilic PVDF composite membrane based on ZrO2–multiwalled carbon nanotubes (MWCNTs) hybrid was prepared by a simple phase-inversion method. ZrO2 nanoparticles were firstly loaded on the surface of MWCNTs via hydrothermal route, which was characterized by Fourier-transform infrared, X-ray diffraction, thermogravimetric analyzer, scanning electron microscopy (SEM), and transmission electron microscopy. It was found that the ZrO2–MWCNTs hybrid formed network structures within the PVDF matrix, avoiding the aggregation of nanofillers. Then, the effects of ZrO2–MWCNTs hybrid on the performances of ultimate PVDF membrane were systematically investigated. The microstructure and surface morphology of novel membranes were observed by SEM and atomic force microscopy. The results indicated that ZrO2 were dispersed homogeneously on the surface of MWCNTs. The as-prepared membrane exhibited enhanced pure water flux and a lower contact angle than those of pure PVDF membrane. Furthermore, the as-prepared membranes processed also improved separation efficiency against oil/water emulsions and achieved better rejection ratio and good durable antifouling performance. In general, ZrO2–MWCNTs/PVDF membrane may provide a potential application against complex oil/water systems.

Facile fabrication of a robust superwetting three-dimensional (3D) nickel foam for oil/water separation

Abstract A superwetting three-dimensional (3D) nickel foam was prepared by a facile electrodeposition process. Wettability, surface morphology, and chemical composition were characterized with contact angle test, scanning electron microscopy, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy, respectively. According to the results, the as-prepared 3D nickel foam presented robust superhydrophobicity and superoleophilicity with good mechanical and chemical stability simultaneously. Furthermore, with the superwetting behavior, the nickel foam showed excellent oil/water separation capability with both high efficiency and lasting recyclability. Besides, the simple, low cost, and environmentally friendly fabrication process endows a scale-up of 3D nickel foam for oil/water separation and pollution disposal of leakage of organic solvents.

Effect of functionalized multi-walled carbon nanotubes on the microstructure and performances of PVDF membranes

Functionalized multi-walled carbon nanotubes (f-MWCNTs) were synthesized by grafting carboxyl groups and 3-aminopropyltriethoxysilane (APTS) on the nanotube surface, respectively. A novel polyvinylidene fluoride (PVDF) membrane was prepared by incorporation of different dosages of APTS modified MWCNTs (A-MWCNTs) via the phase-inversion method. The dispersity of MWCNTs and compatibility between MWCNTs and the polymer matrix were enhanced after functional modification. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) testing showed that A-MWCNTs/PVDF blend membranes exhibited superior surface morphology and pore structure. Because of a strong interfacial interaction with the PVDF matrix, the mechanical strength of PVDF membranes was improved by adding A-MWCNTs and the optimum addition content was 2 wt%. More importantly, the bovine serum albumin (BSA) rejection of membranes increased significantly from 64.2% (nascent PVDF membranes) to 92.48% (A-MWCNTs/PVDF), which was attributed to the network structure of APTS. It can be expected that the blending modification of PVDF membranes by f-MWCNTs will have a bright and foreseeable application prospect.

Enhancing the photocatalytic and antibacterial property of polyvinylidene fluoride membrane by blending Ag–TiO2 nanocomposites

A novel polyvinylidene fluoride (PVDF) ultrafiltration membrane with photocatalytic and antibacterial properties was prepared by phase inversion. The in situ formed silver (Ag) nanoparticles were immobilized with titanium dioxide (TiO2) nanoparticles. And the modified PVDF membranes were fabricated by adding Ag–TiO2 into the casting solution. Results showed that the surface contamination of membrane can be degraded effectively by photocatalysis method. Compared with the pristine membrane, the hydrophilicity of modified membrane was improved. Besides, the modified membrane had an excellent antibacterial property. Therefore, the novel Ag–TiO2–PVDF membrane has a very promising application perspective.

Preparation of a novel anti-fouling β-cyclodextrin–PVDF membrane

As part of this work, polyvinylidene fluoride (PVDF) membranes were prepared via a phase inversion method. A novel β-cyclodextrin (β-CD)–PVDF membrane was prepared via an interfacial reaction, using Trimesoyl Chloride (TMC) and β-CD as cross-linking and modification agents, respectively. The membranes were modified by a simple dip-coating method. The results of comparison between the modified and unmodified membranes by attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) methods confirmed successful grafting of β-CD on the membrane surfaces. The morphology of the membrane was investigated by scanning electron microscopy (SEM) and atomic-force microscopy (AFM). The roughness of PVDF membranes increased after their surfaces were grafted with β-CD. It was also found that β-CD–PVDF membranes had higher permeate flux and hydrophilicity than those of the pristine PVDF membranes. Furthermore, in protein fouling experiments, bovine serum albumin (BSA) was used as a protein model solution. Modified membranes exhibited a higher flux recovery ratio. The experiment showed that the anti-fouling performance of β-CD–PVDF membranes was more effective in reducing the irreversible membrane fouling. The results of this study hold promise for useful applications of β-CD–PVDF membranes in membrane separation areas.

Facile preparation of a smart membrane with ammonia-responsive wettability transition for controllable oil/water separation

Abstract Stimuli-responsive materials with wettability reversal have significant potential for controllable oil/water separation. Herein, an ammonia-responsive cotton fabric membrane was designed by a facile dip-coating approach. The cotton fabric membrane coated with nickel stearate particles presents superhydrophobic and superoleophilic. Interestingly, the membrane turns into superhydrophilic and underwater superoleophobic upon exposure to ammonia vapor. Accordingly, the as-prepared membrane can achieve controllable immiscible oil/water separation with favorable separating efficiency. More importantly, we found it was capable to effectively separate both water-in-oil and oil-in-water emulsions with promising flux and antifouling performance. Furthermore, the fabricating strategy is simple and the raw materials used in the production are not only economic but also environmentally safe, which will provide positive guidance in practical applications.

Novel amino-functionalized Fe3O4/carboxylic multi-walled carbon nanotubes: One-pot synthesis, characterization and removal for Cu(II)

A novel amino functionalized Fe3O4/multi-walled carbon nanotubes hybrid was synthesized by a facile and efficient one-pot solvothermal process. The 3-aminophenoxyphthalonitrile which was regarded as phthalonitrile monomer was introduced into the solvothermal process and promoted the phthalocyanine cyclization reaction, finally forming the amino functionalized hybrid. The structure, composition, and morphology were characterized by FTIR, XRD, XPS, SEM, and TEM. It was found that the monodispersed amino functionalized Fe3O4 spheres with diameters of 180–220 nm were uniformly attached on the surface of multi-walled carbon nanotubes. Owing to the synergistic effect between the amino groups and magnetic carbon nanotubes, the asprepared hybrid exhibited the high separation efficiency when used to remove Cu(II) from aqueous solutions. The adsorption isotherms of the as-prepared hybrid for Cu(II) removal fitted the Langmuir model, the maximum adsorption capacity of our amino-functionalized Fe3O4/MWCNTs hybrid calculated from the isotherm model is 30.49 mg g–1. This work demonstrated that the amino functionalized Fe3O4/multi-walled carbon nanotubes hybrid was promising as efficient adsorbent for heavy metal ions removal from wastewater in low concentration.

Study on the catalytic effect of ErCrO3 nanoparticles on the thermal decomposition of ammonia perchlorate

Orthorhombic structure perovskite ErCrO3 nanocrystals were prepared by glycine combustion method. The ErCrO3 nanocrystals were characterized by XRD, SEM, and BET. The catalytic activity measurements were carried out by DSC and TG-MS. The results indicate that ErCrO3 nanoparticles have an intense catalytic effect on the decomposition of AP. Adding 2% of ErCrO3 obtained product to AP decreases the decomposition temperature by 82°C and increases the heat of decomposition by 0.6 kJ g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, NO, HNO, N2O, NO2, and Cl2. The mechanism of catalytic action is based on the presence of superoxide ion (O2−) and oxygenic ion (O−, O2−) on the surface of ErCrO3, and they can accelerate the thermal decomposition process of AP and the oxidation of NH3.

Attached β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane to graphene oxide and its application in copper removal

The environmental applications of graphene oxide and β-cyclodextrin (β-CD) have attracted great attention since their first discovery. Novel nanocomposites were successfully prepared by using an esterification reaction between β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane grafted graphene oxide (β-CD/GPTMS/GO). The β-CD/GPTMS/GO nanocomposites were used to remove the Cu2+ from aqueous solutions. The characteristics of β-CD/GPTMS/GO were detected by scanning electron microscopy (SEM), Fourier transform infrared, X-ray diffraction (XRD), thermogravimetric analysis (TG) and energy dispersive X-ray (EDX). The dispersibility of graphene oxide was excellent due to the addition of β-CD. The adsorption isotherms data obtained at the optimum pH 7 were fitted by Langmuir isotherm model. The excellent adsorption properties of β-CD/GPTMS/GO for Cu2+ ions could be attributed to the apolar cavity structure of β-CD, the high surface area and abundant functional groups on the surface of GO. The adsorption patterns of β-CD/GPTMS/GO were electrostatic attraction, formation of host-guest inclusion complexes and the ion exchange adsorption. The efficient adsorption of β-CD/GPTMS/GO for Cu2+ ions suggested that these novel nanocomposites may be ideal candidates for removing other cation pollutants from waste water.